There is a machine tool in which a spindle housing supporting a specifically directed spindle for rotation alone is supported for parallel motion in orthogonal three-axis directions XYZ by a numerical control mechanism (see, for example, Japanese Patent Publication No. 2001-9652).
In the machine tool, a work support-feeding device that feed-rotates a work around a specific axis is provided, and machining is carried out by feed-rotating the work at a specific angle position therearound.
To perform such a machining, it is necessary to accurately determine a phase for the work around the specific axis on the work support-feeding device. Therefore, a reference tool for phase determination is formed and installed on the spindle, and thereon, a phase determination operation is performed so as to abut the work. After the operation, the tool is detached from the spindle and stored in a specific position. (See, for example, Japanese Patent No. 3083776.)
In the above-mentioned conventional work phase determination method, working efficiency falls because the operation of mounting/dismounting the reference tool on the spindle is required. In addition, it is uneconomical because a storage space for the reference tool is required. Moreover, there is some fear of shortening bearing life because a load acts on a bearing rotatably supporting the spindle when the work abuts the reference tool.
The present invention aims to solve the above-mentioned problems.